I have written a simple app in Android that uses MediaPlayer API to play a video from a URL. How to calculate Time To First Frame (TTFF)?

Here is my snippet:

        String url ="http://192.168.174.80/video-h264.mkv";
        //.....
        long t0 = System.currentTimeMillis();
        Uri videoUri = Uri.parse(url);
        vw1.setVideoURI(videoUri);

        // Listener for onPrepared() event (runs after the media is prepared).
        vw1.setOnPreparedListener(
                new MediaPlayer.OnPreparedListener() {
                    @Override
                    public void onPrepared(MediaPlayer mediaPlayer) { 
                        // Start playing!
                        vw1.start();

                        mediaPlayer.setOnBufferingUpdateListener(new MediaPlayer.OnBufferingUpdateListener() {
                            @Override
                            public void onBufferingUpdate(MediaPlayer mediaPlayer, int i) {
                                    long t1 = System.currentTimeMillis();
                                    mBufferingTextView.setText((t1 - t0) + " ms,  %" + i + " buffer");
                                }
                            }
                        });
                    }
                });